Muscle Disease Flashcards
What are the main causes of myopathy disorders?
Inflammatory Endocrine disorders Electrolyte/ Metabolic disorders Drugs/Toxins Infection Rhabdomyolysis
How do muscle diseases usually present?
Muscle pain (myalgia)
Muscle weakness/tiredness
Stiffness
Abnormal blood tests
What type of muscle disease are polymyositis and dermatomyositis?
Inflammatory
What gender is more affected by inflammatory muscle disease?
Female:male 2:1
What age group most commonly develop inflammatory muscle disease such as polymyositis or dermatomyositis?
Peak incidence ages 40-50 years
There is an increased incidence of malignancy in inflammatory muscle disease. TRUE/FALSE?
TRUE
What histological features can be seen on muscle biopsy in inflammatory muscle disease?
muscle fibre necrosis
degeneration
regeneration
inflammatory cell infiltrate
What causes inflammatory muscle disease such as polymyositis or dermatomyositis?
cause is unknown
Muscle weakness usually presents asymmetrically and gets better over the course of a few months. TRUE/FALSE?
FALSE
Insidious onset, worsening over months
Usually symmetrical, proximal muscles
What activities do patients commonly struggle with when they have muscle weakness?
difficulty brushing hair
or climbing stairs
What cutaneous sign can be present in dermatomyositis?
Gottrons sign
- erythematous macules over dorsum of digits, and can be over elbows and knees
Heliotrope rash
- erythema of the upper eyelids often with associated oedema and telangiectasia
Shawl sign
- erythematous macules on upper back, shoulders, and back of the neck. Can worsen with exposure to UV
What other organ systems can be involved in inflammatory muscle disease
Lung:
- Interstitial lung disease (10%)
- Respiratory muscle weakness
Oesophageal:
- Dysphagia
Cardiac:
- Myocarditis
Other:
Fever, weight loss, Raynauds phenomenon, non- erosive polyarthritis
By how much do inflammatory muscle diseases increase the rate of malignancy, and who is most at risk?
15% incidence in dermatomyositis
9% polymyositis
Risk greatest in men over 45 years
Risk of malignancy occurs in what type of cancers when associated with inflammatory muscle disease?
Ovarian breast stomach lung bladder colon
What symptoms would you expect to see in the history of patient with inflammatory muscle disease?
tired muscles functional difficulty muscle pain weight loss cough breathlessness Raynauds
What underlying medical conditions should you be aware of when taking a history suggestive of inflammatory muscle disease?
thyroid disease
What medications can cause inflammatory muscle disease?
steroids, statins
=> be aware of patients with underlying conditions that report taking these drugs in Hx
What examinations would you carry out to aid the diagnosis of inflammatory muscle disease?
Confrontational testing
(Direct testing of power)
Isotonic testing
(30 second sit to stand test)
What would you look for in the blood test results of a patient who you think has inflammatory muscle disease?
Muscle enzymes eg. Creatine kinase (CK)
Inflammatory markers
Electrolytes, calcium, PTH, TSH (to exclude other causes)
Autoantibodies: ANA, Anti-Jo-1
What other investigations would you do to potentially diagnose inflammatory muscle disease?
Electromyography
Muscle biopsy
-Perivascular inflammation and muscle necrosis
MRI
-muscle inflammation, oedema, fibrosis and calcification
What treatments can be used for inflammatory muscle disease?
Glucocorticoids Azathioprine Methotrexate Ciclosporin IV immunoglobulin Rituximab
What age group is commonly affected by polymyalgia rheumatica?
Occurs almost exclusively in those over 50 years
What other condition is associated with polymyalgia rheumatica?
Associated with temporal arteritis/giant cell arteritis (15%)
How do patients with polymyalgia rheumatica present clinically?
Ache in shoulder and hip girdle
=> Reduced movement of shoulders, neck and hips
Usually symmetrical
Morning stiffness
Fatigue/anorexia/Weight loss/fever
Muscle strength = NORMAL
